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Old Oct 24, 2012, 09:34 PM
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United States, CA, San Diego
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Good footage again! Excited to see what Rusty is brewing.

Any pictures of your isolator setup, Hansen?

I saw these the other night and thought about giving them a try in place of the EAR grommets, or in junction with. http://www.getfpv.com/featured/orange-rc-bobbins.html Though the EARs are working really well right now with my hard mount. I got rid of a nagging bounce that was actually being caused by the top plate twisting in tilt.

Have you tried those before?
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Old Oct 24, 2012, 10:21 PM
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Hawaii
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>>Any pictures of your isolator setup, Hansen?<<

Sure, attached.

>>I saw these the other night and thought about giving them a try in place of the EAR grommets, or in junction with. http://www.getfpv.com/featured/orange-rc-bobbins.html Though the EARs are working really well right now with my hard mount. I got rid of a nagging bounce that was actually being caused by the top plate twisting in tilt.

Have you tried those before?<<

I have not tried them before. I just ordered 8 of them to try.
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Old Oct 24, 2012, 11:48 PM
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United States, TX, Seguin
Joined Mar 2005
611 Posts
Hansen, I also lowered my Ki and Kp settings in both rate and attitude, after watching your last couple of videos I figured that might be why my copter in the wind would oscillate a bit. It felt like it flew pretty well tonight, though there really wasn't much of any wind, and it still flew calm / smooth enough for my liking which is why I've kept my settings a little higher in the past (not looking for aerobatic performance on this copter).

I have a pin at the ready but it would seem to need 2 to make it really secure, one for the top clamp block and one for the bottom. I can make it work on the top block but not sure I can get one into the bottom block (the rear CF plate has a hole in it at the same level as the block but it is off center). I had the thought that maybe I could put a pin in the top and have a wire loop or carabiner that attaches to part of the roll cage.

In other news I got the roll belt tightened up tonight, just need to put the gimbal back on the copter and see if it's better. I will do that tomorrow, hopefully outside if I get home early enough.
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Old Oct 25, 2012, 12:08 AM
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Hawaii
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>>I also lowered my Ki and Kp settings in both rate and attitude<<

I am going to do that plus I need to go back to smaller diameter propellers. My dog chewed one of the bottom prop so I am using a 13" prop on the bottom.

I have some 12" wood props for top and bottom to try tomorrow.

Andrey and Gary have really good results with the wood props in the wind.

>>I have a pin at the ready but it would seem to need 2 to make it really secure, one for the top clamp block and one for the bottom. I can make it work on the top block but not sure I can get one into the bottom block (the rear CF plate has a hole in it at the same level as the block but it is off center). I had the thought that maybe I could put a pin in the top and have a wire loop or carabiner that attaches to part of the roll cage. <<

I think a safety wire to hold the top and bottom will be fine. It is not like the tube will fall out for no reason. You just don't want it falling out at the wrong time. A safety wire would be enough.

>>In other news I got the roll belt tightened up tonight, just need to put the gimbal back on the copter and see if it's better. I will do that tomorrow, hopefully outside if I get home early enough.<<

The weekend is coming.
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Old Oct 25, 2012, 08:58 AM
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when we had "training" on adjusting timing belts for optical readers they gave us a little routine to follow. When you hold the drive pulley and rotate the driven pulley back and forth the top section of the belt will tighten and slacken. Measure the vertical height the belt travels while doing this and it should be no more than 1/32". Too tight and the belt wears prematurely as well as bushings. More slack and you lose the precision. After your final adjustment did it work out to be about this amount of slack? May be slightly different for this type setup.
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Old Oct 25, 2012, 01:36 PM
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I wouldn't worry too much about the bearings wearing out from too much tension. This isn't an industrial application. You'll crash a long time before MTBF. I would take all the slack out for the best precision.
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Old Oct 25, 2012, 01:40 PM
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Originally Posted by SeismicCWave View Post
Yes the jitters will show up on the video footage.
Do we know this *for sure*? As it been done properly, and proven to not work?

I guess I just have trouble with the concept that a belt suddenly removes jitters, when no geartrain could.

For example, what if you are considering a 3:1 belt reduction, and then two servos. Either a 0.06sec/60 10Kg-cm servo, and one of the same brand but 0.18sec/60 30Kg-cm. It seems to me that you should get the same resolution and jitter levels if you use the 0.06sec servo with a belt drive, as you would using the 0.18sec servo direct. It's just a question of where are the gears, in the case, or external? The final gear ratio from motor to camera is the same in both cases.

What if you used a really slow sail winch servo? Or a Servo City Power Servo Gearbox with 3:1 gearing. Not as good as a belt?
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Old Oct 25, 2012, 02:09 PM
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Hawaii
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>>Do we know this *for sure*? As it been done properly, and proven to not work?<<

Yes absolutely. Many times.

>>I guess I just have trouble with the concept that a belt suddenly removes jitters, when no geartrain could.<<

It has nothing to do with the belt removing jitters. It has to do with power of the drive train. A hobby servo is designed to handle a fairly light inertia. Light load such as control surfaces of a fixed wing aircraft. Even quarter scale aircraft has relatively light inertia in regards to load.

A camera on a gimbal is a totally different animal. When you move a heavy inertia the load will "bounce" when you stop. The servo will try to stop the bounce. Digital servos are the worse. Coreless servos are just as bad.

That's the reason for belt or gear drive. Gear drive has some backlash and will show up on the video footage. Belt drive is better but you can also get the belt bounce. However with a high enough ratio you are really trading off servo speed with torque. That is that is the reason for the smoothness issue.

>>For example, what if you are considering a 3:1 belt reduction, and then two servos. Either a 0.06sec/60 10Kg-cm servo, and one of the same brand but 0.18sec/60 30Kg-cm. It seems to me that you should get the same resolution and jitter levels if you use the 0.06sec servo with a belt drive, as you would using the 0.18sec servo direct. It's just a question of where are the gears, in the case, or external? The final gear ratio from motor to camera is the same in both cases.<<

Exactly, if you find a servo powerful enough to hand the load without belt and without back lash the result will be the same.

>>What if you used a really slow sail winch servo? Or a Servo City Power Servo Gearbox with 3:1 gearing. Not as good as a belt?<<

I have thought about sail winch servo a lot. They are powerful but they are slow and heavy. So I have never tested them. Servo City gearbox will also work if you can get rid of the back lash and if they are not heavy.

The belt system is NOT the only system that works. It is for the time being the only system that is:

1) Light
2) Simple
3) Smooth

There are others that are continuing their research on things like direct drive brushless motors with special controllers. One day we may see something different.
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Old Oct 25, 2012, 02:29 PM
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Quote:
Originally Posted by R_Lefebvre View Post
I wouldn't worry too much about the bearings wearing out from too much tension. This isn't an industrial application. You'll crash a long time before MTBF. I would take all the slack out for the best precision.
Remember these are not industrial grade servos either They don't like a lot of radial pressure on the shaft. Maybe a nice spring loaded idler or an auto tensioner built into the servo mount would be good to incorporate into the design to remove the slack. Rusty?
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Old Oct 25, 2012, 03:21 PM
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Hawaii
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Quote:
Originally Posted by pug398 View Post
when we had "training" on adjusting timing belts for optical readers they gave us a little routine to follow. When you hold the drive pulley and rotate the driven pulley back and forth the top section of the belt will tighten and slacken. Measure the vertical height the belt travels while doing this and it should be no more than 1/32". Too tight and the belt wears prematurely as well as bushings. More slack and you lose the precision. After your final adjustment did it work out to be about this amount of slack? May be slightly different for this type setup.
I think that is a good way to check belt tension. I have tried different belt tension and the difference is not really that noticeable. You do not want belt tension that is either too loose or too tight. The 1/32" vertical height for the 120 groove belt we use seems very reasonable.

I have run the belt tension as loose as when I move the gimbal the tooth will skip to as tight as a drum where you can "twang" the belt.

You are right about the servo shaft cannot handle too much tension. That's why Servo City sells servo blocks to relieve the strain on the servo shaft.
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Old Oct 25, 2012, 04:25 PM
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Navarre, FL
Joined Mar 2002
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Quote:
Originally Posted by pug398 View Post
Maybe a nice spring loaded idler or an auto tensioner built into the servo mount would be good to incorporate into the design to remove the slack. Rusty?
The G10 servo mount has some flex to it, so consider that you're auto tensioning device

Rusty
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Old Oct 25, 2012, 05:26 PM
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Hawaii
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Vibration isolator tests

Rusty made me work. He was questioning the effectiveness of Sorbothane so I had to do some tests to show myself that it works.
20121025 Bouncing ball test (0 min 18 sec)
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Old Oct 25, 2012, 05:54 PM
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United States, OR, Portland
Joined Feb 2012
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Sorbothane is the bee's knees for copter vibrations. I tested a crazy amount of material in rusty's original floating plate before settling on sorbothane. While I have just gotten started taking videos, I have hundreds of tack sharp photos since "padding up" as I pictured in Rusty's thread. I used to have problems with side to side play with the old floating plate but with the new round style it is fantastic.

Here is my workhorse quad rigged up like the Y6 in Rusty's thread. I am always amazed when I touch the camera with the quad hovering and find I can't feel any vibration at the camera.

IMG_8799 by supergravy, on Flickr
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Old Oct 25, 2012, 08:02 PM
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VA
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I will have to agree sorbothane is the "bomb"

here is a pic of a antivibe plate for an IMU module that uses sorbothane and works fantastic. Planning to increase the size of the bumbers and use the same principle for the gimbal.
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Old Oct 25, 2012, 08:08 PM
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BelgiŽ, Vlaams Gewest, Evergem
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Where can I get this gimbal?
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